0651-0660

651. 4 Keys Keyboard $\star\star$

652. Find Duplicate Subtrees $\star\star$

653. Two Sum IV - Input is a BST $\star$

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class Solution {
 public:
  bool findTarget(TreeNode* root, int k) {
    vector<int> nums;

    inorder(root, nums);

    int l = 0;
    int r = nums.size() - 1;

    while (l < r) {
      int sum = nums[l] + nums[r];
      if (sum == k) return true;
      if (sum < k)
        ++l;
      else
        --r;
    }

    return false;
  }

  void inorder(TreeNode* root, vector<int>& nums) {
    if (!root) return;

    inorder(root->left, nums);
    nums.push_back(root->val);
    inorder(root->right, nums);
  }
};

654. Maximum Binary Tree $\star\star$

655. Print Binary Tree $\star\star$

656. Coin Path $\star\star\star$

657. Robot Return to Origin $\star$

658. Find K Closest Elements $\star\star$

659. Split Array into Consecutive Subsequences $\star\star$

660. Remove 9 $\star\star\star$